Lung disease undiscovered for many long-term smokers

(HealthDay News) -- Millions of long-term smokers may have undiagnosed lung disease, according to a study published online June 22 in JAMA Internal Medicine.

The study involved 8,872 people between the ages of 45 and 80 who had smoked at least one pack of cigarettes daily for 10 years. Most smoked more than one pack per day, but about half of them were considered disease-free based on spirometry results.

When the researchers used additional criteria to assess the participants' lung function, such as computed tomography scans, use of respiratory medication, and quality-of-life issues, they found most of those considered "disease-free" had some sort of lung impairment. Lung scans found emphysema or airway thickening in 42 percent of those thought to be free of lung disease. Meanwhile, 23 percent of the participants had significant shortness of breath compared to almost 4 percent of those who never smoked. The researchers also found that 15 percent of those in the study took six minutes to walk about 1,000 feet, compared to 4 percent of nonsmokers. Smokers who thought their lungs were fully functioning also had much worse quality of life than those who didn't smoke.

"Based on these results, we project that there are 35 million current and former smokers older than 55 years in the United States who may have unrecognized disease or impairment," the authors write. "The effect of chronic smoking on the lungs and the individual is substantially underestimated when using spirometry alone."